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Skin-Melanocytic Tumors
Blue nevus - Variants
Last major update: November 2008 - next update November 2009
Revised: 18 September 2009
Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.
Copyright (c) 2002-2009, PathologyOutlines.com, Inc.
Atypical cellular blue nevus, Cellular blue nevus, Epithelioid blue nevus, Malignant blue nevus
Terminology
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● Atypia insufficient for definitive diagnosis of malignancy
● Experienced dermatologists frequently disagree on this diagnosis (AJSP 2008;32:36)
Case reports
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● 37 year old woman with thigh mass (J Dermatol 2000;27:730)
● Presenting as vascular lesion of back (Ann Pathol 2000;20:228)
Treatment and prognosis
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● Treat conservatively with excision
Micro description
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● Infiltrative margin or asymmetry, cellular atypia, prominent nucleoli, mitotic rate of less than 2 per square millimeter
Additional references
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Sites
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● Buttock and sacrococcygeal areas are most common
● Also scalp, face, dorsal hands and feet
Epidemiology
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● Benign, but rarely recurs or involves regional lymph nodes
● Melanomas may arise from cellular blue nevus (controversial)
Case Reports
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● Case of the Week #7 / Dermatology Case of the Month #1
● Nevus cells in sentinel lymph node (Eur J Dermatol 2008;18:586)
● Eyelid tumors (J Am Acad Dermatol 2008;58:257)
● With pilonidal cyst (J Cutan Pathol 2007;34:942)
● 14 year old boy with giant, infiltrative, facial tumor (J Clin Pathol 2007;60:82)
● 31 year old man (Indian J Dermatol Venereol Leprol 2001;67:200)
● 28 year old woman with intracranial extension (J Clin Neurosci 2000;7:453)
Treatment and prognosis
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● Excision
Clinical description
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● Amelanotic tumors have atypical clinical appearance
● Note: benign cellular blue nevi may involve lymph node parenchyma and sinuses in a metastatic-like pattern; as a result, some tumors are best classified as having “uncertain biologic behavior”
● Large (> 1.5 cm) with intense pigmentation
Micro description
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● Well circumscribed collection of interweaving fascicles with increased cellularity and extension into subcutis
● Heavily pigmented spindle cells alternate with clear cells
● Have pushing margins and variable fasciculation and neural structures
● No/minimal atypia; no junctional activity, no epidermal invasion, no peripheral inflammation, no necrosis, no/rare mitotic figures
● Scalp lesions may have intracranial extension
● “Ancient” blue nevi show stromal changes of large dilated vessels with pseudoangiomatous features, hyaline angiopathy, myxoid changes, sclerosis or hyalinization of stroma, variable edema, similar to ancient melanocytic nevi (Am J Dermatopathol 2008;30:1)
● Variants include amelanotic (AJSP 2002;26:1493) or with balloon cell change
Micro images
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Congenital tumor Permeating along hair follicle Infiltrating skeletal muscle
(inset: Fontana Masson stain)
Low power images
Medium power High power images
High power images
Contributed by Angel Fernandez-Flores, MD, PhD, Hospital El Bierzo and Clinica Ponferrada, Spain
Positive stains
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● HMB45, MelanA/Mart1, variable S100
● CD34 (J Cutan Pathol 2001;28:145)
Negative stains
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● No/low Ki-67
Molecular / cytogenetics
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● No chromosomal aberrations (AJSP 2005;29:1214)
Video
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● YouTube
Differential Diagnoses
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● Malignant blue nevus (scalp or heel lesion with marked nuclear atypia, numerous mitotic figures, some atypical, and necrosis; variable epithelioid tumor cells)
Epidemiology
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● Very rare
● May be part of Carney complex, which includes cardiac myxoma, psammomatous melanotic schwannoma, multicentric blue nevi, endocrine overactivity (Orphanet J Rare Dis 2006 Jun 6;1:21); may also occur by itself (Am J Dermatopathol 2000;22:473)
● May be a low grade melanoma; 60% have nodal metastases, but clinical course is otherwise indolent
● May involve genital mucosa (Br J Dermatol 2001;145:496)
Case reports
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● 2 year old boy with congenital giant melanocytic nevus on back and no evidence of Carney complex (Am J Dermatopathol 2002;24:30)
● Involving oral mucosa (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003;96:429)
Micro description
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● Poorly circumscribed but symmetric heavily pigmented dermal lesion
● Short fascicles, small nests and single cells
● Composed of both (a) heavily pigmented and globular melanocytes and (b) lightly pigmented and polygonal or spindle melanocytes
● No/rare mitotic figures
● Usually no maturation and no dermal fibrosis
Epidemiology
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● Very rare
● Melanoma arising in background of cellular or common blue nevus or resembling a blue nevus
● Often in children or in scalp
● May be present for many years before rapid growth occurs
● Highly aggressive (AJSP 2001;25:316); may recur locally, extend into brain (if from scalp or eyelids), metastasize and cause death
Case reports
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● 5 year old girl (Croat Med J 2005;46:463)
● 11 year old girl with malignant blue nevus of left ear, associated with large nevus at same location and 2 intracranial melanocytic tumors (Hum Path 2004;35:1292)
● 41 year old man (Am J Dermatopathol 2003;25:21)
● 55 year old man with scalp lesion, nodal and distant cutaneous metastases (Am J Dermatopathol 2007;29:88)
● With nodal metastases (J Cutan Pathol 2008;35:651)
● Scalp tumor with distant skin metastases (Am J Dermatopathol 2007;29:88)
● In keloid scar (J Plast Reconstr Aesthet Surg 2008 Jan 7 [Epub ahead of print])
Treatment and prognosis
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● Excise and examine carefully
Micro description
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● Expansile asymmetric nodule with benign component OR low power benign features plus infiltrative borders, necrosis, mitoses or atypical cytologic features
● May have epithelioid features with large hyperchromatic nuclei, prominent nucleoli and cytoplasmic melanin
● Note: benign cellular blue nevus may involve lymph node parenchyma and sinuses in a metastatic-like pattern; some blue nevi are best classified as having “uncertain biologic behavior”
Micro images
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Various images
Differential Diagnoses
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● “Animal/equine” melanoma - infiltrative, aggregates along follicles, cells resemble melanophages but all cells are melanoma cells after bleaching
End of Skin-Melanocytic Tumors > Blue nevus - variants
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